Method of and apparatus for heating coiled strip metal



HEATING COILED STRIP METAL Patented Jan. 2.4, 1950 ME'rHn oF ANDAPPARATUS Fon HEA'rmG 1 coman s'rmr METAL /f Lee Wilson, Rocky River,Ollio Application December s1, 1946, serial Nin-"nasse This inventionrelates to heating coiled strip metal, and more particularly to animproved' method of and apparatus for annealing or otherwise heattreating strip steel or the like in coils while protecting the surfacesof the strip from corrosion, scaling, de-carburization, or othervundesirable effects. I

Itis a usual practice to anneal strip'steel in coils and frequently,such as in brightf'annealev ing, it is desirable to protect the coilfrom contact with atmospheres which may harmfully affect the stripsurfaces during the annealing operation, Furnaces of the Well-known bellorco'ver type are particularly well adapted for this type of heattreating and various means have been proposed for protecting the coilsby maintaining an atmosphere of a protective gas around the coil whileit is being raised to the desired temperature and cooled. Onearrangement which has been successfully and extensively used for thispurpose in cover type furnaces includes an inner shell or cover ofrelatively light gauge metal which is placed over a coil, or stack ofcoils, as the coil rests upon the furnace base with its axis verticallydisposed. These protective covers fit loosely over and are spaced fromvthe coil and means are provided for directing a protective atmosphereup through the furnace base into the hollow center of the coil andpermitting it to ll the space within the cover and escape around itsbottom edge. However, although' such protective covers achieve excellentresults they constitute an item of continuing expense as they arerelatively short lived because of the repeated handling in normal useand continued exposure to high temperatures for long periods of time indirect contact with the furnace atmosphere with resulting warping andcorrosion.

It is, therefore, among the objects of my present invention to provide amethod of and appara- 9 Claims, (CL 26H3).

a volume of protective gas is required: the provision of a furnace andcoil support combination for heating coiled strip metal which obtainshigh heating efficiency at lowrst cost and operating expense, permitsrapid heating` and cooling of the coils, and produces a uniform highquality product: the provision of a simple and rugged structure vforsupporting and protecting coils against harmful atmospheres which may beemployed eithegjn direct or indirectly heated furnaces; and theprovision of heating apparatus tus for heating -coiled strip metal in afurnace,

while protecting the strip from contact with harmful atmosphere, inwhich the use of the usual coil covers is eliminated and in which heatmay effectively be applied to'th'eridsof coil for most emcient heatingthereof. ',15'5 l,

Other objects of my invention include; thezprovision of heatingapparatus for coiledstrp metal in which the outer layer of the coilitself serves as a protective sheath for the inner coil layers ;orconvolutions; the provision of a coil heating apof the type describedwhich reduces to a minimum the time and labor involved in setting up acoil prior to placing a furnace bell thereover.

The above and other objects of my invention will appear from thefollowing description of several embodiments thereof, reference beinghad to the accompanying drawings in which:

Figure 1 is a vertical cross sectional view through a bell type furnacein which my improved coil supporting and protecting arrangement isincorporated.

Figure 2 is a detached side elevation of a coil of strip metal, the freeouter end of the coll being secured to the adjacent surface of the coilin a somewhat modified manner from that shown in Figure 1.

Figure 3 is an enlarged fragmentary top view of the coil shown in Figure1, taken on line 3 3 of Figure 1. Figure 4 is a horizontal crosssectional view taken on line -t of Figure 1.

Figure 5 is a view generally similar to Figure 2 but illustratinganother modified arrangement for maintaining the outer end of the stripin close engagement with the adjacent surface of the coil.

Figure 6 is a view generally similar to Figure 5 but illustrating athird modification of the means for closing or sealing the outer freeend of the coil.

Figure 'I is a fragmentary top view of a coil with the outer end of thestrip free.

. ary supporting base. Preferably supported above paratus in which thecontact of undesirable gas atmospheres with the surfaces of the strip inthe .mil :nay effectively be prevented without the use oi special coilenclosures or the like and which the furnace base structure, and inspaced ,relationthereto, I provide a coil carrying plate having agenerally iiat upper surface of slightly larger area than the end areaof the largest coil to be supported thereon. Means are provided fordirecting a protective atmosphere up through a centrally located inletport in this plate. The

coil to be heated is placed on this supporting plate "i afieatci orcarrier in up-ended position with its axis extending vertically andsubstantially aligned with the center of the plate so that the outeredge of the plate extends beyond the outer edge of the end of the coil.Next an upper cover plate ls placed on the top of the coil. This plateextends beyond the outer edge of the top end of the coil and the outerend of the metal strip is preferably substantially sealed against theadjacent outer layer of the coil to prevent circumferential ilow of theoutside atmosphere into the coil convolutions. Thus, when the coil issupported as described and a protective gas is discharged into thecenter of the coil and permitted to escape between the top and bottomend surfaces of the coil and their respective cover plates, access ofharmful gases to all parts of the coil is prevented except to the outerside surface thereof. After the annealing orother heat treatingoperation is completed the outer convolution of the coil may, ofcourse,be oxidized but the remaining strip in the coil will be in the desiredcondition having been protected during the heating operation and it isonly necessary to cut oif and discard from the outer end of the coil alength equal substantially to the outer circumference of the coil.

Referring to the accompanying drawings, a furnace bell or cover isindicated at F and includes a supporting frame structure I and arefractory lining 2. It will be understood that the furnace isdiagrammatically illustrated and that, although a relatively small unitadapted to heat only a single coil is illustrated, the furnace might beenlarged to accomodate any desired and practical number of coils in asingle charge. Fuel burners 3 and 4 .discharge downwardly through thetop of the furnace bell structure toward the top of the coil C and aresupplied with fuel from the feed lines and 6 respectively. Although theillustrated furnace is provided with three top burners arrangedsymmetrically around the vertical center line of the bell (the thirdburner not being shown in the drawings) it will be understood that anydesired number of burners may be employed and that the location of theburners in the furnace may be varied to achieve the most efficientheating results.

Supported above the foundation line 1 on suitable structural members 8is the stationary furnace base generally indicated at B. In theapparatus illustrated this base is circular in form and is provided witha refractory section 9 and an annular sealing trough III. Acorresponding annular sealing flange II is carried by the bottom of thefurnace bell F and a suitable sealing material I2, such as sand orwater, is disposed in the trough I0 in well-known manner. When the bellis in operating position as shown in Figure 1 the flange II, incooperation with the trough I0 and sealing material I2, provides asubstantially gas tight seal between the furnace base B and the bell Fwhile permitting the bell F readily to be lifted fro-m and replaced ontothe base, `An eye or lifting ring I3 secured to the top of the framestructure I facilitates handling of the furnace bell.

The bottom coil supporting and end covering plate I4 is supported onstanchions I5, I6, and

I1 which, as is best seen in Figure l, preferably have their lower endsmounted in socket members I8. Bottom burners I9, and 2| extend upwardlythrough the base B and are supplied with fuel through suitable pipes asindicated at I9' and 20'. These burners are preferably 4/ symmetricallyspaced around' the vertical center line of the base B in the same manneras the top burners previously described and the discharge with thebottom burners I9, 20 and 2I is directed upwardly against the under sideof the coil supporting plate I4.

A suitable source of supply of protective gas is connected to the supplypipe 22 which extends up through packing gland 23 and the base B intothe center gas inlet port 24 in the plate I4. It will be observed thatthe plate I4 is recessed on its under side to provide sockets for theupper ends of the stanchions I5, I6 and I1 and that the bottom coilsupporting plate can be removed by merely lifting it off of thesupporting stanchions. Although the pipe 22 has a substantially gastight connection with the plate I4 it is not securely attached thereto.

The coil being annealed, generally indicated at C, is positioned on thebottom plate I4 with its central axis substantially aligned with thecenter of the plate I4. Thus, as is clearly seen in Figure 1,' thehollow center 25 of the coil C will receive the protective gasdischarged through the port 24. To control and restrict the flow ofprotective gas through the port 24 and to protect the strip edgesurfaces which make up the upper end 26 of the coil C, I provide a topcover plate 21 which is preferably substantially the same size and shapeas the bottom plate I4 except that it is imperforate and may be providedwith lifting rings 28 and 29 to facilitate handling. Top and bottomplates I4 and 21 are preferably made of a suitable high temperaturealloy and are sufficiently thick to prevent excessive and undesirablewarping when repeatedly subjected to furnace temperatures.

In operating the apparatus described above the desired protective gas isdischarged through the pipe 22 and the port 24 into the hollow center 25of the coil C. This gas is maintained under greater pressure than thatwhich exists outside of the coil C. Due to normal variations in stripwidth and in winding the coil, a completely gas tight fit between thebottom end of the coil C and the substantially flat upper face of plateI4 and between the upper end of coil C and the substantially flat bottomface of plate 21 is not practicable. Thus the protective gas ispermitted to escape across the ends of the coil, as indicated by thesmall arrows in Figure 1, and effectively prevents the entry ofundesirable atmosphere between the cover plates and the ends of thecoil.

In order to prevent or limit the entry of outside atmosphere into thecovolutions of the coil C at the outer end 30 of the strip I preferablyprovide means for maintaining the outer end of `the strip sealed to orin close engagement with the adjacent surface of the coil. I haveillustrated several ways in which the end of the strip may be maintainedin the desired position, Figures 1 and 3 showing a' continuous Weld 30between the end 30 of the coil and the adjacent outer layer 32. InFigure 2 a series of spot welds 33 secure the outer end of the strip inplace during the heating operation while Figure 5 illustrates a coilwhich has been bound by metal bands or straps 34, 35, and 36 which holdthe end 31 of the coil in close engagement with the coil body. Amodification of the arrangement shown in Figure 5 is illustrated inFigure 6 in which a pressure distributing bar 38 extends bestantialentry of outside atmosphere between the outer layer of the coil and thenext adjacent inner layer.

When welding is employed to seal the end of the strip against the bodyof the coil, as shown in Figures l, 2 and 3, it is necessary to cutthrough the outer layer of the coil in order to permit it to be unwoundand cut off after the heating operation is completed. With the bandingarrangement shown in Figures 5 and 6, it is only necessary to cut thebands and then unwind and cut ofi7 the exposed outer layer of the strip.By securing the outer end of the strip against the body of the coil,entry of harmful gases into the coil convolutions is substantiallyprevented and the amount of protective atmosphere which is required toprevent oxidation of the coil is maintained at a minimum. However` itwill be understood that in some cases it may be practical to leave theouter end of the strip free as iis-indicated in Figure 7 and to dependentirely on supplying enough protective gas to the interior of the coilto prevent damage to the strip surfaces during heating. When the outerend of the strip is left free it is possible `that the outsideatmosphere will work into the coil for a limited distance, butwith sometypes of material the outer layer will hug the body of the coil suf-`application the con is assemmed with top and bottom cover plates andplaced on suitable sup portsln the furnace and connections made to asource of protective gas.

i'lciently tightly to restrict the entry of outside B to the header 46which in turn connects with a discharge ue tl. The top burners 3 and 4and the third burner of the top' set (not shown) discharge downwardlyagainst the top plate 21 and thus this plate is heated directly byconvection as well as by radiation from the furnace walls, etc. Theproducts of combustion from the top burners move downwardly around theouter surface of the coil C and, together with the By 'providing top andbottom end covers for the coil and maintaining a. `iiow of inert orprotective gasinto the center of the coil and out between the ends ofthe coil and the covers, I have completely eliminated the necessity forseparately enclosing the coils in a separate sheath or cover in' which.the protective atmosphere is maintained. My arrangement not onlysubstantially reduces operating costs by saving the expense ofmaintaining and renewing the coil covers but also reduces the timerequired for loading and unloading the furnace and, by improving theheating emciency by more direct application of heat to the coil, reducesthe heating time cycle and substantially increases the possible outputof a given furnace installation.

Although I have described the illustrated embodiments of my invention inconsiderable detail, it will be understood by those skilled in the artthat variations and modifications may be made in the arrangement andproportions of the ,parts making up my improved apparatus and in theprocedure employed in carrying out my method without departing from thespirit of my invention. I do not, therefore, wish to be limited to themethod and apparatus herein particularly disclosed but claim as myinvention all embodiments thereof comingwithin the scope of the appendedclaims.

I claim:

1. Apparatus for protecting coils of strip metal during annealing orother heat treatment comprising two end covers, each having asubstantially fiat coil engaging face, said faces having greater areathan the ends of the coil to which they are to be applied whereby theywill completely cover said ends, means for substantially sealing theouter free end portion of saidv coil against the next below layer ofsaid coil, and means for discharging gas under pressure into the hollowcenter of said coil.

2. In combination with a coil of strip metal having its outer free endportion held in close engagement with the next below layer of said coil,a cover plate in engagement with and subproducts of combustion from thebottom burners id, 2d and 2i, flow out through the nues 42, I3, it andt5.

As both the bottom and top coil cover plates iii and 2li are subjectedto direct heat from the burners and are in direct contact with the coilends, the coil is most advantageously heated because the major heatinput is through the ends of the coil. It is now recognized that suchapplication of heat to a coil provides more efclent heating than theapplication of heat through the outer side surface of the coil. It willbe understood that, although I have illustrated and described a directred furnace in which my top and bottom coilA cover plates and the outersurface of the coil are exposed directly to the products of combustion,my invention is Vequally applicable to use with furnaces employingradiant tubes, electrical heating ele'-, ments, or muiiie arrangementsin which the products of combustion are prevented from directlycontacting the coil. Furthermore, my coil protecting apparatus may beused with box type'.

furnaces in which the coil is moved into and out' of the furnace heatingchamber. In such an stantially completely covering one end of said coil,a second cover plate in engagement with and substantially completelycovering the other end of said coil, and means for discharging gas underpressure into the hollow center of said coil, said cover platespreventing the escape of said gas from said hollow center except betweensaid coil endsl and the inner coil engaging surfaces of said coverplates.

3. Apparatus for protecting a coil of strip metal during annealing orother heat treatment thereof comprising a pair of end cover plates forsaid coil, one of' said plates being adapted to support said coil in`up-ended -position and cover the bottom end thereof and the other ofsaid plates being adapted to'rest upon and cover the top end of saidcoil,` one'of said plates having an aperture therethrough, and means fordischarging gas under pressurethrough said aperture into the hollowcenter of said coil, said plates having nonsealing engagement with theends of said coil -wherebyigasdischarged into thecenter of said coil mayiescape'between the ends of said coil and said plates th" "by preventingthe entry of outside atm(Vis-.pli re etween said plates and the ends .of.I i

aaeaei 4. In combination in apparatus for heating coils of strip metal,a bottom coil supporting and end covering plate, a top end cover plateadapted to rest upon and cover the top end of a coil when said coil issupported on its bottom end on said bottom plate, said bottom platehaving a gas port extending therethrough, said plates having non-sealingengagement with the ends of said coil, means for discharging aprotective gas through said port into the hollow center of a coildisposed on said bottom plate, and furnace means for heating saidvplates and a coil disposed therebetween.

5. In apparatus for heating coils of strip metal, the combination of afurnace base, a bottom coil supporting and end covering plate having asubstantially horizontal top surface of larger area than the coilsupported thereon, said bottom plate having a gas port extendingtherethrough, means -for supporting said plate above and in spacedrelation to said furnace base, means for conducting gas under pressureto said gas port, a top coil covering plate adapted to rest upon andcover the top end of a coil when said coil is supported by said bottomplate, a removable furnace bell adapted to be positioned on said furnacebase over said coil covering plates and a coil disposed therebetween,and means for heating the interior of said furnace bell.

6. The method of protecting a coil of strip metal against contact withan undesirable atmosphere which includes the steps of substantiallysealing the outer free end portion of the strip against the next belowlayer of the coil. covering the ends of said coil and leaving the sidesurface thereof exposed, maintaining a desired atmosphere within thehollow center of said coil under greater pressure than that which existsoutside of said coil, and permitting said desired atmosphere to escapeacross the ends of said coil.

7. The method of heating a coil of strip metal which includes the stepsvof substantially sealing the outer free end portion of the strip againstthe next below layer of the coil, covering the ends ol the coil andleaving the side surface thereof exposed, directing protective gas intothe hollow center of said coil at greater pressure than that whichexists outside of said coil, and heating said coil in a furnace whilemaintaining said protective gas within said coil at greater pressurethan that which exists outside of said coil.

8. The method of heating a coil of strip metal which includes the stepsof substantially sealing the outer free end portion of the strip againstthe next below layer of the coil, supporting the coil on a base platewith the coil axis vertical, covering the upper end of the coil by a topplate in direct contact therewith, enclosing the coil and plates withina furnace, applying heat to said plates and to the side surface of saidcoil, and

maintaining a gaseous atmosphere within the hollow center of the coil atgreater pressure than that which exists within the furnace outside ofthe coil whereby said gaseous atmosphere is caused to escape into thefurnace between said plates and the top and bottom ends of said coil.

9. In combination an apparatus for heating coils of strip metal, abottom coil supporting and end covering plate adapted to support andcover the bottom end of a coil, a top end cover plate adapted to restupon and cover the top end of a coll supported by said bottom plate,said bottom plate having a gas port extending therethrough, said plateshaving non-sealing engagement with said coil ends, and means fordischarging protective gas through said port into the hollow center ofthe coil disposed on said bottom plate.

' LEE WILSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 138,060 Waters Apr. 22, 18731,960,808 Cope May 29, 1934.

